Method of manufacturing sulfuric acid.



I. P. LIHMB.

METHOD OF MANUFACTURING SULFURIG ACID.

APPLICATION FILED JUNE 12,1913.

1,103,522. Patented July 14, 1914.

z Z tn as; a: 27 14622502 decomposed by sulfuric acid could be con Yunnan STATES PATENT oFFIcE.

IENS P AUIJI LIHME, OF LAKEWOOD, OHIO, ASSIGNOR TO THE GRASSELLI CHEMICAL COMPANY, OF CLEVELAND, OHIO, A CORPORATION OF OHIO.

METHOD OF MANUFACTURING SULFURIC ACID.

To all whom it may concern:

lie itknown that I, IENs PAVLI Liimn, a citizen of the United States, and a resident of Lakewood, county of (luyahoga, and State of Ohio, have invented a new and useful Improvement in Methods of Manufacturing Sulfuric Acid, of which the following is a specification, the principle of the lIl vention being herein explained and the best mode in which I have contemplated applying that principle, soas to distinguish it from other inventions.

The present invention, relating as indicated to the manufacture of sulfuric acid, has more particular regard to the improvement of the so-called contact process of manufacturing sulfuric anhydrid and sulfuric acid. Such contact process involves the converting of sulfur dioxid and oxygen from the air into sulfnrtrioxid by means of platinum in a finely divided state, and has been known and used with more or less success for a'nnmber of years. The diiliculties militating against the successful use of the process are due to impurities in the gases as the latter leave the burners, for if these im purities are not absolutely removed before the gases enter theplatinum contact, the catalytic action of the latter will, in a shorter or longer time, entirely stop. The impurities which have to be dealt with are, first, solid matters, such as flue dust and sulfuric acid in the form of spray, carried along with the gases; and, second, much the more difficult to remove, are the impurities thatare carried along in a gaseous state, such as arseniurcted, seleniureted and phosphurcted hydrogen", also'chlorids and other hydrogen gases, which are not soluble in sulfuric acid or water. The presence of these impurities in the burner gases has been demonstrated by lViukler, who, in his experiments in regard to contact sulfuric acid, proved that arseniureted hydrogen (AsI-L) besides sulfureted hydrogen are present in burner gases, and that both are detrimental to platinum as contact material. Knietsch worked out the contact sulfuric acid process for the Badische Anilin & Soda Fabrik, and he found that notwithstanding that the gases were originally pure, nevertheless the contact material was poisoned with arsenic, which proved that only gaseous arsenic. combination which could not be Specification of Letters Patent.

Patented July ii, ism.

Application filed June 12, 1913. Serial No. 773,233.

sidered. These arsenical compound gases have been proven to be ASH The presence of Asll, is explained by the presence of metal, such as iron, in contact with sulfuric acid containing arsenious' acid, As,O,,, hydrogen being generated and combining with arsenic to form arsen-iureted hydrogen.

Various methods have been employed in an attempt to prevent the formation of the arseniureted hydrogen, such as removing all iron, where apt to come in contact with acid containing arsenic, and substituting lead or earthenware, or brick lining, but such methods have not met with any great success. The present method and apparatus have rather been designed with a view to eliminating or removing such arsenimreted' hydrogen as may be formed, and so bring only gases that are entirely free fromthis impurity into contact with the platinum.

The steps and. details of apparatus for carrying out my improved method will hereinafter be fully described and particularly pointed out in the claims.

The annexed drawing and the following description set forth in detail certain steps and an approved form of mechanism embodying the invention, such disclosed means constituting, however, but one of various ways in which the principle of the invention may be carried out. In said annexed drawings-1 igure 1 is a plan view of. a plant or apparatus for manufacturing sulfuric acid by the contact process embodying my present improvements; Fig. 2 is a transverse section through the part of such apparatus, specifically designed for the removal of the arseniureted hydrogen; and Fig. 3 is a plan view of a detail showing a modification.

For purifying the gases as they come from the burners, as is well known, two methods are in general use, onea wet, and the other a dry method. \Vhile my invention may be adopted inthe wet process to advantage, it is especially beneficial in cdnnection with the dry method of purifying the gases when ores containing arsenic are burned, and 'the specific apparatus illustrated in the drawing is designed. for use in such dry method of purification. In this process, it is a Well known fact that the iron contact .shaft does not retain all of the arsenic from the ore, even where the latter is very small in quantity; the consequence 45 it is also provided with steam coils 14, preftowers and through dry filters consisting of- 'is that arsenic trioxid (As O is carried over into the first absorption tower where, in contact with acid and iron, the arseniureted hydrogen is formed. Even where the gases from such first absorption tower are subsequently passed through drying boxes filled with porous material, such as slag, as is done in certain systems, the arseni-ureted hydrogen is not removed, since it exists in a gaseous state and so passes on, ultimately reaching the platinum, which'it renders inactive. By experiment and investigation, however, I have found that such arseniureted hydrogen-and other similar obnoxious gases, such as those previously mentioned, can be removed from the gases by means of iron or copper oxid heated to a temperature not to exceed 100 centigrade, a temperature of 70 to 90 centigrade, be ing preferred. It is not desirable to employ higher temperatures than those named, since the purification is otherwise incom plete.

1 thereof will be seen to illustrate in general, an arrangement of furnace 1, iron contact tower 2, cooler. 3, and primary absorptlon towers 4, such as are 1n familiar use.

After leaving the absorption towers the gases are nextconductedthrough slag filter boxes 5, such as are referred to above as being employed in the known dry processes of purifying the gases. I do not, however, conduct the gases directly from such dry filter boxes to the platinum contact chamber, the latter being included in the tower. '2 as usual; but I first pass the same through an iron shaft or tower 6 provided with grate bars 7 adapted to support the iron or copper oxid, which is used as the arseniceliminatingmedium, (see Fig. 2). This tower 6 is arranged with hoppers 8 on top for charging fresh material into the same, as shown in the sectional View of Fig. 2, and

.erably several coils under the grate bars, for heatin maintain t1e desired temperature. A certain number of coils be placed on top ,of the preceding filter boxes 5, if desired, to insure the gases being at approximatelyv the proper temperature when they reach the iron shaft, my experiments having demonstrated the maintenance of the temperature to be an important item in the successful carrying out of my method of purification. Preferably additional filter boxes 9, similar to filter boxes5, are installed in the path of the gases after they leave thisspecial iron shaft; the total number of such filter boxes, in otherwords,

should aggregate the number at present in use, this part of the operation being conducted in two stages W1th' my special puri Having reference to the drawing, Figure the contents of the tower to (not shown) may also fication step interposed, as it were. From the last-named set of filter boxes-the gases are conducted by a pipe 10 to the-platinum contact chamber, thence they are carried by a pipe 11 to the second cooler 12 and the final absorption towers 13, as heretofore.

By the foregoing arrangement I have found, by careful tests under actual operating conditions, that a gas is obtained absolutely free from gaseous arsenic and other obnoxious compounds; as also one absolutely free from any trace of sulfuric acid, which is apt to be carriedover as a mist with the gases from the preceding wash tower.

It is to be observed that my process is distinguished from other processes, whereby it has heretofore been attempted to remove arsenic from burner gases used in the manufacture of sulfuric acid, in that such present process recognizes the presence of the arsenic in gaseous form namely as arseniureted hydrogen. No method or process herev tofore devised, as far as I am aware, is capable of achieving the result which I have accomplished. l

The reaction that occurs in the. tower 6, I have found results in the production of a certain amount of water owing to the combination of some of the hydrogen from the arseniureted hydrogen with oxygen from the oxide. In case the quantity-of water is sufli'cient to render its removal desirable, v

a lead tower 16 (Fig, 3) may be interposed between said tower 6'and the next adjacent filter box 9. The tower 16 will be filled with coke or like material and sulfuric acid be allowed to trickle down thereover so as to absorb all moisture in'the gases leaving-the purification step.

my invention may be employed instead of the one explained, change being made as regards the steps or mechanism herein disclosed, provided the means stated by any Other modes of applying the principle of of the following claims or the equivalent of such stated means be-employed.

distinctly claim as my invention v 1. In a method of manufacturing sul- I therefore particularly point out and l furic anhydrid and acid, the step which grade,

consists in passing the burner gases, at a temperature between 70 and 90 centiin contact with iron oxid.

4:. In a method of manufacturing sulfuric anhydrid and acid, thesteps which consist in filtering the sulfur-011s burner gases at a temperature not exceeding 100 centigrade; passing such gases in contact with a metallic oxid capable of absorbing hydrogen compounds .of arsenic and the like; further filtermg such gases; and. then subjecting the same to the catalytic action of platinum.-

5. In a method of manufacturing sul- .ing arseniureted hydrogen; mg such gases;

furic anhydrid and acid, the steps which consist in filtering the. sulfurous burner gases; passing such gases, at .a temperature between 70 and 90 centigrade, in contact with a metallic oxld capable of absorbfurther filterand then subjecting the same to the catalytic action of platinum.

Signed by me, this 10th day of June, 1913;

' I. PAULI LIHME.

Attested bya JNo. F. OBEBLIN,

W. R. GRIBBEN. 

